1. Field of the Invention
The present invention relates to a power supply apparatus and a vehicle using the same.
2. Description of the Related Art
In recent years, a hybrid electric automobile is developed and has begun to be served to a practical use. FIG. 1 shows an example of a power supply apparatus installed into the hybrid electric automobile. The hybrid electric automobile using the power supply apparatus is comprised of a main battery (BATT) 10, a junction box (J/B) 20, a power drive unit (PDU) 30, a motor 40, an auxiliary battery 60, a load 70, an electronic control unit (ECU) 80 and a DC-DC converter 90.
The main battery 10 stores and outputs the DC power of as high voltage as 144 V. The output of the main battery 10 is supplied to the power drive unit 30 and the DC-DC converter 90 via the junction box 20.
The junction box 20 accommodates a main switch 21, fuses 22 and 23, a main contactor 24a, a sub-contactor 24b, a resistor 25 and a switch 26. The main switch 21 and the fuse 22 are inserted in series on a current path in the main battery 10.
The main switch 21 is of a manual operation type and is used to stop the output of the main battery 10 compulsorily in case of check of the vehicle. The fuse 22 fuses when over-current flows through the main battery 10, and stops the output of the main battery 10 compulsorily. The fuse 23 is provided for the current path on the input side of the DC-DC converter 90, and fuses when over-current flows through the DC-DC converter 90, and stops the power supply to the DC-DC converter 90 compulsorily.
The main contactor 24a is a 2-terminal switch and is inserted between the output terminal of the main battery 10 and the input terminal of the power drive unit 30. Also, the resistor 25 and the switch 26 connected in series are inserted in parallel to the main contactor 24a. The sub-contactor 24b is also a 2-terminal switch and is provided for the current path between the negative terminal of the smoothing condenser 31 and the negative terminal of the main battery 10.
The power drive unit 30 is comprised of an inverter circuit 30a which converts DC power from the main battery 10 into 3-phase AC power. The smoothing condenser 31 is connected with the input terminal in parallel to the inverter circuit 30a. The smoothing condenser 31 is provided to restrain rush current flowing through the power drive unit 30 in case of power-on. The 3-phase AC power outputted from the power drive unit 30 is supplied to the motor 40. The motor 40 has a generator function of AC power in addition to the motor function, and the rotation axis is connected with a crankshaft of an internal combustion engine (not shown). When operating as the motor, the motor 40 is rotatively driven by the 3-phase AC power from the power drive unit 30 to rotate wheels (not shown) through a gear machine and to help the drive of the internal combustion engine. Also, when operating as the generator, the motor 40 is rotatively driven by the internal combustion engine (not shown) and generate AC power. The AC power generated by the motor 40 is converted into the DC power through the inverter circuit 30a and the smoothing condenser 31 and is used to charge the main battery 10 directly, and charges the auxiliary battery 60 through the DC-DC converter 90.
As described above, the DC-DC converter 90 converts the high voltage DC power generated by the motor 40 and smoothed by the smoothing condenser 31 into low voltage DC power. Also, the DC-DC converter 90 converts high voltage DC power sent from the main battery 10 via the junction box 20 into low voltage DC power. The auxiliary battery 60 and the load 70 are connected with the output of the DC-DC converter 90. The auxiliary battery 60 is charged with the low voltage DC power outputted from the DC-DC converter 90.
Also, the load 70 is such as an air conditioner, wipers and so on, and are driven by the low voltage DC power from the auxiliary battery 60 and the DC power from the DC-DC converter 90. The electronic control unit 80 is composed of a microprocessor and controls the whole power supply apparatus.
The operation of the conventional hybrid electric automobile using the power supply apparatus formed as described above, especially, the operation upon start-up will be described.
When an ignition key (not shown) is operated, the main switch 21 is turned on and the electronic control unit 80 turns on a relay RY1 and a relay RY3 to set the switch 26 and the sub-contactor 24b in the junction box 20 to the ON state. By this, the DC power from the main battery 10 charges the smoothing condenser 31 via the resistor 25 and the switch 26 and is supplied to the power drive unit 30. Because the current supplied to the power drive unit 30 is limited by the resistor 25, the charging operation to the smoothing condenser 31 is gentle.
When the smoothing condenser 31 is charged to a predetermined voltage, the electronic control unit 80 sets the relay RY2 to the ON state and the relay RY1 to an OFF state. The relay RY3 continues the ON state. Thus, the main contactor 24a is set to the ON state and the switch 26 is set to the OFF state. In this way, the DC power from the main battery 10 is directly supplied to the power drive unit 30 via the main contactor 24a. The inverter circuit 30a carries out a switching operation to the DC power to convert the DC power from the main battery 10 into 3-phase AC power, and the power drive unit 30 supplies the 3-phase power to the motor 40. Thus, the motor 40 is rotatively driven.
On the other hand, the DC-DC converter 90 converts high voltage DC power from the main battery 10 or the smoothing condenser 31 into low voltage DC power and supplies to the auxiliary battery 60 and the load 70. Thus, the auxiliary battery 60 is charged and the drive of the load 70 becomes possible.
As described above, the conventional hybrid electric automobile using the power supply apparatus is comprised of the resistor and the switch to charge the smoothing condenser gently. Because large current flows through the resistor and the switch in the high voltage, a high breakdown voltage and a breakdown current are required to the resistor and the switch. As a result, the resistor and the switch become expensive and the manufacturing cost of the power supply apparatus rises.
In conjunction with the above description, an electric system of an electric automobile is disclosed in Japanese Laid Open Patent application (JP-A-Heisei 5-344605). The electric system of the electric automobile in this reference is comprised of a main battery for vehicle drive, an auxiliary battery for auxiliary units and an inverter which has a smoothing condenser. The power is supplied to an AC motor for the vehicle drive from the main battery through the inverter. The initial charging circuit of the input condenser is comprised of an insulation type combination reactor, a semiconductor switching device connected between the primary side of the combination reactor and the auxiliary battery, and a rectifier connected between the secondary side of the combination reactor and the inputting condenser. The input condenser is charged in the initial stage by the initial charging circuit.
Also, an electric system of an electric automobile is disclosed in Japanese Laid Open Patent application (JP-A-Heisei 6-54410). The electric system of the electric automobile in this reference is comprised of a main battery for vehicle drive and an auxiliary battery for auxiliary units. The power is supplied to an AC motor for the vehicle drive from the main battery through an inverter. The auxiliary battery is charged by the AC output from the inverter. Also, the DC-DC converter using the auxiliary battery as a power supply carries out an initial charging operation to an input condenser in case of start-up of the inverter.
Also, a control system of an electric automobile is disclosed in Japanese Laid Open Patent application (JP-A-Heisei 10-304501). The control system of the electric automobile in this reference is comprised of an inverter which converts DC power of a main battery into AC power and drives a running motor. A main contactor is provided between the main battery and the inverter. A precharge contactor is provided between the main battery and the inverter. A control unit closes a precharge contactor to precharge a condenser and closes the main contactor when determining that the precharge has ended. A current sensing station detects precharge current. The control unit determines that the precharge has ended when the precharge current is lower than a reference value after a predetermined time from the start of the precharging operation.
Also, a power supply apparatus of a hybrid electric automobile is disclosed in Japanese Laid Open Patent application (JP-A-Heisei 11-8910). In the power supply apparatus of this reference, a main battery charges an auxiliary battery through a DC-DC converter. A high voltage circuit section carries out a so-called inverter operation and supplies AC power to a coil on the side of the large number of turns of a transformer in case of power supply from the main battery to an auxiliary battery, and carries out a rectifying operation in case of power supply from the auxiliary battery to the main battery. A low voltage circuit section carries out a rectifying operation in case of power supply from the main battery to the auxiliary battery, and carries out the inverter operation and supplies AC power to a coil on the side of the small number of turns of the transformer in case of power supply from the auxiliary battery to the main battery. According to the power supply apparatus, the power transmission from the auxiliary battery to the motor for engine start can be realized with a simple circuit.
Also, a hybrid electric automobile is disclosed in Japanese Laid Open Patent application (JP-A-Heisei 11-164494). The hybrid electric of this reference is comprised of a high voltage drive main battery which is driven in a high voltage and which supplies power to an engine start motor and a running motor, and an auxiliary battery which is driven in a low voltage and which supplies power to an auxiliary unit. An average charging power transmission section transmits power to one of both of the batteries. A control unit controls the average charging power transmission section such that one of the both batteries charges the other.